Why does the Audi A6 have better fuel efficiency than other luxury sedans?

I've heard that the Audi A6 has exceptional fuel efficiency compared to other luxury sedans in its class. Can anyone explain why?

The Audi A6 utilizes a mild hybrid electric drivetrain, which allows it to seamlessly switch between electric and gasoline power, resulting in improved fuel efficiency.

Audi uses a fuel-saving technology called ''cylinder on demand'' in some A6 models. This engine system shuts down four of the engine's eight cylinders when they're not needed, saving fuel in the process.